This means that it can't connect to the database, period. So check your database authentication string. Make sure that your SQL server is in fact finch13.com or cubemail.finch13.com and not "localhost" or something else.

cPusername = your cPanel usernameroundcubeUser = The name of the user you assigned to the roundcube databasepaassword = Your database user passwordroundcubeDB = The name you assigned the database you created for roundcube

The cPanel username and an underscore (_) gets added to every database username and database you create automatically.